Motor vehicle brakes often utilize a plurality of opposing, pairs of pads on brake calipers to frictionally engage a rotor disc which is secured to and rotates with a vehicle wheel in a manner well known in the art. Preferably the braking surfaces of the rotors are planar and are oriented to be perpendicular to the axis of rotation of the vehicle wheel. Brake rotors are typically disc-shaped structures having two oppositely facing ring-shaped planar braking surfaces. Ideally, these two ring-shaped braking surfaces should be parallel, perfectly planar and should be mounted with respect to the axis of rotation of the vehicle wheel so that the two rotating parallel surfaces are perpendicular to the axis at all times.
In practice this ideal configuration is difficult to realize because the stacked tolerances of the hub and rotor assemblies, known in the industry as the "hubless rotor," frequently cause a wobbling of the disc brake rotor on the mounted running assembly, a condition that is commonly referred to as "run-out." In recent years, automobile manufacturers have been plagued with an increased incidence of excessive run-out, which commonly manifests itself in the form of increased brake pedal pulsation problems. Excessive run-out results in reduced braking efficiency and often in the premature wearing out of the brakes. Lateral disc run-out refers to lateral deviation of the planar surface of a rotor along a radial line perpendicular to the longitudinal axis of rotation of the rotor from a plane extending through the radial line and perpendicular to the axis of rotation. The lateral run-out may not be the same on the two oppositely-facing planar braking surfaces defined by the brake rotor and, therefore, the run-out on each side must be measured and eliminated for proper brake functioning.
A number of devices have been devised and are well known in the art to help correct defects and deviations in the surfaces of brake rotors. One example is U.S. Pat. No. 4,165,662 to Besenbruch et al. which is directed toward a work holder assembly including adapter members having conical faces for engaging a disc brake therebetween or for engaging in a central hole of a disc. A rigid circular plat, with spaced threaded adjustable bolts bears on the face of the disc. Spacer members bear against the circular plate while the adapter members, plate and spacer members are disposed in axial alignment on the shaft. The rigid circular plate and adjustment bolts hold the work piece in axial alignment with the shaft, and correct distortion in the disc or end wall of the drum while preventing vibration of the work piece during dressing.
Another device is shown in U.S. Pat. No. 4,455,900 issued to Callanan et al. for a brake lathe used for refinishing the inner cylindrical surface on a brake drum of the two outer side surfaces on a brake disc. The brake lathe has an indexable spindle so that its tool slide only needs to move in one direction so that the part being worked upon, be it a brake drum or a brake disc, can be oriented to the direction of movement of the tool slide.
Another device for turning a brake surface is disclosed in U.S. Pat. No. 3,691,880 issued to Ratteree et al. which describes a method and apparatus for turning the braking surfaces of a vehicle lug supported braking member, such as a brake drum or disc brake. The brake turning method includes the steps of supporting the braking member on a refinishing lathe so that its lug holes are concentric with respect to the rotational axis of the lathe, rotating the braking member, and engaging the braking surface of the member with the lathe cutting tool maintained at selected distances from the axis of rotation to redefine the braking surface concentric with respect to the circle defined by the lug holes in the braking member. The apparatus includes a backing plate which is carried by the lathe which defines an annular groove in the working face adapted to lie behind the lug holes and a clamping plate also adapted to be carried by the lathe in juxtaposition with the backing plate. The clamping plate is provided with a plurality cf support pins arranged to project through the lug holes of the braking member which is positioned between the clamping and backing plates to position the member concentrically about the rotational axis of the lathe.
A swing arm brake lathe is described in U.S. Pat. No. 5,099,728 issued to Thiem. The brake lathe is for machining both brake drums and brake rotors wherein the tool carriage assembly is pivotable through an arc of about ninety degrees which allows the tool carriage to engage the friction surfaces of either a brake drum or rotor on a fixed spindle. In the drum machining position, the tool carriage assembly is approximately parallel to the axis of the spindle and when in the disc machining position the tool carriage assembly is approximately perpendicular to the axis of the spindle. The lathe further includes alignment means to assure proper alignment of the tool carriage assembly without the spindle, and release means to remove the tool carriage assembly from the remainder of the lathe for service.
U.S. Pat. No. 4,493,231 issued to Wossner describes a method and device for machining brake discs while the discs are still on the vehicle. The refacing of the worn brake discs is accomplished by connecting an outer drive with the disc or with the shaft on which the disc is mounted. This positions the machine tools with respect to the disc for refacing the disc. Two adjustable tools are fixed on a common transverse carriage and simultaneously machine two faces of the disc. Coupling and centering devices are arranged on either side of the refacing device and may be coupled consecutively with the disc on the two sides of the vehicle.
Other examples of machines and methods for correcting brake problems include U.S. Pat. No. 5,095,786 issued to Belinghausen et II., U.S. Pat. No. 4,266,454 issued to Mitchell et al., U.S. Pat. No. 3,260,137 issued to Obmann and U.S. Pat. No. 3,540,165 issued to Lanham. The '786 patent is directed to a method and apparatus for dampening brake lathe vibration. The '454 device discloses a method and an apparatus for dampening vibrations during the turning of a rotor by means of a pair of weights which respectively lie in inclined tracks and are held against the opposite faces of the disc by the force of gravity. The '137 patent discloses a device for unbalance correction of rotors and the '165 device is directed to rotatably holding a braking member having opposed braking surfaces for machining the surfaces.
The prior art does not provide an effective way to eliminate a common and potentially destructive problem; namely, the problem of how to easily eliminate disc brake rotor run-out. The present invention discloses a device and a method using the device for measuring a rotor for evidence of run-out before the rotor is removed from the vehicle, accurately marking the high portion of the rotor surface and then marking both the rotor and a portion of the vehicle hub to enable a service technician to replace the rotor in the same orientation after it has been removed and lathed to resurface the rotor. The inventive device enables the service technician to easily remove the surface defects on the rotor and comprises a brake lathe adapter that includes an adapter mounting, arbor and two pairs of adapter plates which are mounted on the adapter mounting arbor, each pair of adapter plates comprising a fixed plate and a rotatable plate. The fixed plates are mounted toward the respective ends of the mounting arbor and the moveable plates are mounted inside the fixed plates. Each plate has one offset or angled flat side surface that has been machined or cut at a one degree (1.degree.) angle and the pairs of plates are arranged on the mounting arbor so that the angled sides are adjacent. The rotor is mounted between the two movable inner plates and they are rotated on the mounting arbor to compensate for the rotor run-out before a rotor surface is lathed.